What are the two classes of pumps in engineering?

In engineering, pumps are primarily classified into two broad categories based on their operating principles: positive displacement pumps and centrifugal pumps.

Positive displacement pumps function by trapping a fixed amount of fluid and forcing it through the pump's outlet. This action creates a specific flow rate irrespective of the system pressure, making them suitable for applications requiring a consistent and high-pressure output. They can be further divided into gear pumps, diaphragm pumps, and piston pumps, among others.

Centrifugal pumps, on the other hand, utilize rotational energy to move fluid. They increase the fluid's velocity and convert this kinetic energy into pressure. This type of pump relies on the continuous supply of fluid to operate effectively, as it does not trap fluid volumes in the same way positive displacement pumps do. Centrifugal pumps are appreciated for their ability to handle large volumes of low-viscosity fluids efficiently.

The classification mentioned captures the essential differences in operation and application, providing a foundational understanding of pump types that are critical in various engineering scenarios. This distinction helps engineers to choose the appropriate pump type based on the requirements of flow rate, pressure, and fluid characteristics in their specific applications.